In the past, an optical cable has been provided with a given radius of curvature to avoid characteristic degradation and damage. Therefore, when an extra length of the optical cable is handled, the optical cable is coiled into a loop.
As a mechanism for handling an extra length of an optical cable, a mechanism provided with slits radially provided in a mounting plate, a sliding section that is slid able back and forth along each slit, and a cable holder attached to the sliding section is known (see, for example, Japanese Laid-open Patent Publication No. 62-164005).
FIG. 21 is a perspective view for describing an example of handling of an extra length of an optical cable.
FIGS. 22 to 24 are front views for describing an example of a method for unlocking a cable holder.
As depicted in FIG. 21, to the input and output side of an optical module 602 placed on a substrate 601, an optical cable 200 is connected. The optical cable 200 is held by a plurality of cable holders 603 disposed on the substrate 601. Moreover, an extra length of the optical cable 200 is handled by being coiled into a loop by the optical module 602.
The cable holders 603 are fixed to the substrate 601. The cable holders 603 are mounted on the substrate 601 in advance to provide a given radius of curvature of the optical cable 200. Moreover, to absorb extra length tolerances of the optical cable 200 by moving the cable holders 603, extra mounting holes for the cable holders 603 are provided in the substrate 601.
As depicted in FIGS. 22 to 24, when the optical cable 200 is taken out of the cable holders 603, lids 603b fitted in holder main bodies 603a are individually unlocked by a human hand 604.
Incidentally, with an increase in traffic, the density of communication devices is increasing year after year and demand for smaller communication devices has grown recently. As a result, the sizes of devices on a printed-wiring board increasingly become smaller, and the number of optical cables handled on the printed-wiring board is increased.
Therefore, as in the above-described mechanism for handling an extra length of an optical cable, in a mechanism in which slits and sliding sections are provided in a mounting plate and cable holders are attached to the sliding sections, a component mounting area and a pattern area are limited on the substrate which is the mounting plate. This hinders high-density mounting.
Moreover, the plurality of cable holders 603 depicted in FIGS. 21 to 24 are disposed in accordance with the route of the optical cable 200. This increases the number of places where the cable holders 603 are fixed to the substrate 601 and accordingly limits the component mounting area. As a result, high-density mounting of the substrate 601 is hindered.